Employees may use cocaine, but the truth--it is not a drug that sticks around very long in the body making it detectable like Marijuana (which may linger in the fat tissue or urine for up to 30 days). A DOT drug test of a late night employee, perhaps someone who came on the graveyard shift after partying with other drug using friends, may be a candidate for a reasonable suspicion drug test, but it is unlikely Cocaine will prompt reasonable suspicion. It is more likely to be hyperactivity, possible intoxication on the job due to alcohol use, which has more behavioral signs and symptoms that will trigger the request.
Cocaine was first used as an anesthetic in eye surgery in the 1880's. It constricts blood vessels while providing a topical anesthetic. Softer drugs eventually made it obsolete. Novocaine was one such drug. Cocaine is often diluted with a variety of substances before being sold. This could be almost any inert white powdery substance. Not a good thing for Cocaine users to be sure.